Magnetic un loader



March 17, 1936. c 1 P A Re. 19,893

MAGNETIC UNLOADER Original Filed Feb. 2'7, 1951 2 Sheets-Sheet l 1 1 4 AI l 1 l I I l 1 A l AA I I I v v I 1 v v I 1 I v y v v 1 I I I v Ir vMazatr: 'gzfipaas I Carfifl? WM, M meawww March '17, 1936.

C. ELL. LIPMAN MAGNETIC UNLOADER 1 Original Filed Feb; 27, 1951 2Sheets-Sheet 2 Reissued Mar. 17, 1936 UNITED STATES PATENT OFFICEMAGNETIC UNLOADER Carl E. L. Lipman, Chicago, Ill., assignor, by mesneassignments, to Serve], Inc., a corporation of Delaware Original No.1,899,341, dated February Serial No. 518,746, February 27, 1931.

Application for reissue April 27, 1934, Serial No.

12 Claims.

This invention relates to refrigerating systems of the compressorcondenser evaporator type. In this type of refrigerating system and moreparticularly in this type of system wherein the motor compressor is ahermetically sealed unit, it is desirable and in some instancesnecessary for the proper and successful operation of the system, tosubstantially equalize the pressures upon the high and low sides whenthe compressor is started.

The purpose of this is to reduce the resistance to starting of the motorcompressor unit and thereby reduce the load upon the motor at starting.This permits the use of a motor of minimum capacity for the actual workduring running periods which is also very desirable in sealed units. Itis also necessary of course to prevent the warm refrigerant from passingback through the suction line to the low side and into the evaporatorbetween running periods or when the pressures upon the high and lowsides of the compressor are equalized. Otherwise the reverse flow ofrefrigerant will transfer heat to the expansion or evaporating elementand result in a considerable loss in efficiency.

It is therefore an object of this invention to provide in arefrigerating system of the above character means for materiallyreducing the pressure in the high side of the system when the compressoris stopped or just before restarting without allowing the refrigerantunder low pressure to enter the low side as far back as the expansion orevaporating element.

In accordance with this invention advantage is taken of the increase ofcurrent during starting of the motor compressor unit to causesubstantial equalization of pressures upon the low and. high sides ofthe compressor. in units in which the oil and. refrigerant is dischargedtogether over the motor, advantage is also taken of the oil drippingfrom the motor to cooperate with the unloading valve to cause the sameto seal tightly during normal running periods of the motor compressorunit.

Other and further objects and their advantages resulting from thisinvention will be apparent as the same becomes better understood from anexamination of the specification and claims in connection with theaccompanying drawings, wherein:

Fig. 1 is a transverse vertical section through a motor compressor unithaving incorporated therein an unloading device constructed and arrangedin accordance with this invention.

Fig. 2 is a diagrammatic illustration of a re- Furthermore,-

frigerating system having incorporated therein a motor compressor unitincluding an unloader device embodying the features of this invention.

Fig. 3 is a transverse section taken on line 3-3 of Fig. 1 with themotor elements removed.

Fig. 4 is a fragmentary detail taken on line 4-4 of Fig. 1.

Fig. .5 is a fragmentary section taken on line 5-5 of Fig. 1.

Fig. 6 is a fragmentary detail taken on line 6-6 of Fig. 1.

Referring more particularly to Fig. 2, it will be seen that therefrigerating system includes a hermetically sealed motor compressorunit I which delivers refrigerant under pressure through pipe 2 to thecondenser '3 for liquefying the same. The liquid refrigerant then passesthrough float chamber 4, through pipe 6, to the evaporator 1 after whichthe vaporized refrigerant is withdrawn from evaporator I through a checkvalve 8 and is returned to the suction side of the compressor throughpipe 9. In the illustrated motor compressor unit, the lubricating oil iscirculated in part at least through a cooling coil ll and is returned tothe unit and discharged in part at least through the center of the motorshaft with the refrigerant. The oil thus circulated will drain down overthe motor.

With particular reference to Fig. 1, it will be seen that the motorcompressor unit illustrated is mounted upon a base 12 and ishermetically sealed by means of a cup-shaped casing or dome I3, the openend of which is secured and sealed to a base I2. The unit itselfcomprises a compressor l4 driven by an electric motor comprising astator l6 and a rotor 11. A three phase induction motor has been foundfactory driving motor. The compressor is arranged to receive refrigerantthrough an inlet or suction duct l8 formed in the base and to dischargethe same into the interior of the dome and to circulate a portion or allof the lubricating oil through a center bore IS in the shaft. Thelubricant is thrown outwardly against a bafile or distributor 2| andfalls down over the stator to the base of the motor, being collected ina Well or sump 23. It will be understood that inasmuch as the interiorof the dome receives the compressed refrigerant it is therefore underthe pressure of the compressed refrigerant.

Normally upon stopping of the driving motor the refrigerant upon thedischarge side of the compressor and within the casing I3 is underrelatively high pressure whereas the refrigerant a very satisupon thesuction side of the compressor is a relatively lower pressure. Atstarting, this condition would necessitate that the compressor bestarted under load against the high pressure of the discharge side. Inorder to eliminate this load or "unload the compressor means areprovided for equalizing the pressure or at least substantially reducingthe pressure of the discharge side of the. condenser. For this purpose aconnection 24 is made into duct l8 which leads through pipe 26 to avalve 21 communicating with the interior of the dome or high pressureside. Valve 21 is conveniently secured by a bracket 28 to the spider 29supporting the stator of the driving motor. The valve includes a fiatsided closure member 3| slidlngly mounted within casing 21 to permitpassage of gas therebetween when in open position. The upper end of thevalve interlocks through a loose connection with an annular tray-likeactuating member 32 of magnetic material which underlies the statorcoils in the direct path of the magnetic field emanating from the same.The actuating member is secured to an arm 33 which is pivoted at 34 tothe spider 29.

The tray member 32 is also arranged to catch a certain amount of the oildripping from the stator coils. The oil collected by the tray will passthrough the loose connection of the valve member where it is interlockedto the tray and will pass down the sides'of the valve member 3| andeffectively seal the seating end.

It can be seen from the foregoing description that valve 21 with itsclosure member 3| will, when the valve is open, connect the suction sideto the interior of the shell and thereby equalize the pressures on bothsides of the compressor. Check valve 8 will prevent the gases frompassing back through the system beyond that point.

It is well known that the starting currents of an electric motor evenwhen unloaded and more so when loaded are materially higher or greaterthan the normal running current. The mass of the tray-like actuatingmember is sufficient to maintain the tray in its lowermost position andthereby hold the valve closed and with 011 therein their combinedweights are more than suificient to hold the tray in its lowermostposition with the normal running current passing through the statorcoils. The weight, however, is not sufflcient to maintain the traymember in lowermost position against the strong effect of the abnormalfield caused by the increased starting currents through the statorwindings. Upon starting therefore the increased field set up by thehigher currents passing through the stator windings will cause thetray-like member to be raised thus raising the valve closure member 3|to equalize the pressures upon both sides of the compressor. If themotor has been standing idle for a considerable length of time the oilwill have drained out of the tray-like member sealing the valve andlightening the actuating member which will even further insure theimmediate raising thereof when starting the motor.

It will be seen from the foregoing description that there has beenprovided an unloading device particularly well adapted for hermeticallysealed motor compressor units inasmuch as the valve and actuatingmechanism are conveniently located within the sealing dome. Furthermore,the unloader requires no external source of power for operation butworks automatically upon the starting of the unit.

It is obvious that many changes may be made in the details ofconstruction without departing from the spirit and scope of thisinvention as defined by the claims.

I claim:

1. In a refrigerating device, a refrigerant circulatory system includinga heat exchange element, a condenser, and a compressor, an electricmotor for driving said compressor, a connection from the high pressureside of the compressor to the low pressure side thereof, a valve in saidconnection, an actuating member of magnetic material for said valvedisposed adjacent the stator of said motor in position to be affected bythe field emanating therefrom, said actuating member being of sufficientweight to be unaffected by the normal field emanating from said statorbut to be moved by the abnormal field caused by starting currentsthrough said stator.

2. In a refrigerating device, a refrigerant circulatory system includinga heat exchange element, a condenser, and a compressor, an electricmotor for driving said compressor, a connection from the high pressureside of the compressor to the low pressure side thereof, a valve in saidconnection, a tray-like actuating member of magnetic material for saidvalve disposed adjacent the stator of said motor in position to beaffected by the field emanating therefrom.

3. In a refrigerating device, a refrigerant circulatory system includinga heat exchange element, a condenser, and a compressor, an electricmotor for driving said compressor, a connection from the high pressureside of the compressor to the low pressure side thereof, a valve in saidconnection, an annular tray-like actuating member for said valvedisposed beneath the stator of said motor and arranged to receivelubricating oil dripping from said stator.

4. In a refrigerating device, a refrigerant circulatory system includinga heat exchange element, a condenser, and a compressor, an electricmotor for driving said compressor, a connection from the high pressureside of the compressor to the low pressure side thereof, a valve in saidconnection, an annular tray-like actuating member for said valvedisposed beneath the stator of said motor and arranged to receivelubricating oil dripping from said stator, said actuating member beingloosely connected to said valve to operate the same and to permit theoil collected therein to flow around said valve to seal the latter.

5. In a refrigerating system, a compressor, an electric motor fordriving said compressor, an evaporator for receiving refrigerant fromsaid compressor, a check valve in the suction line between saidevaporator and said compressor, a connection from the high pressure sideof said compressor to the low pressure side thereof between said checkvalve and the compressor, a valve in said connection, and meansresponsive to the increased magnetic field around the motor and set upby the starting current of said motor for controlling said valve.

6. In a refrigerating system, a compressor, an electric motor fordriving said compressor, an evaporator for receiving refrigerant fromsaid compressor, a check valve in the suction line between saidevaporator and said compressor, a connection from the high pressure sideof said compressor to the low pressure side thereof between said checkvalve and the compressor, a valve in said connection, and meansresponsive to the starting current of said motor for controlling saidvalve, said means comprising a movable member of magnetic materialdisposed in the path of the magnetic field emanating from said motorelements.

7. In a refrigerating system, a compressor, an electric motor fordriving said compressor, an evaporator for receiving refrigerant fromsaid compressor, a check valve in the suction line between saidevaporator and said compressor, a connection from the high pressure sideof said compressor to the low pressure side thereof between said checkvalve and the compressor, a valve in said connection, and meansresponsive to the starting current of said motor for controlling saidvalve, said means comprising a tray-like pivoted lever disposed beneathsaid motor and in position to be affected by the field emanatingtherefrom.

8. In a refrigerating system, a compressor, an electric motor fordriving said compressor, an evaporator for receiving refrigerant fromsaid compressor, a check valve in the suction line between saidevaporator and said compressor, a connection from the high pressure sideof said compressor to the low pressure side thereof between said checkvalve and the compressor, a valve in said connection, and meansresponsive to the starting current of said motor for controlling saidvalve, said means comprising an annular tray-like member disposedbeneath a stator of said motor and in position to be affected by thefield emanating therefrom.

9. In a refrigerating system, a compressor, an electric motor fordriving said compressor, an evaporator for receiving refrigerant fromsaid compressor, a check valve in the suction line between saidevaporator and said compressor, a connection from the high pressure sideof said compressor to the low pressure side thereof between said checkvalve and the compressor, a valve in said connection, and meansresponsive to the starting current of said motor for controlling saidvalve, said means comprising a pivoted annular tray-like member disposedbeneath a stator of said motor and in position to be affected by thefield emanating therefrom.

10. In a refrigerating system, a compressor, an electric motor fordriving said compressor, an evaporator for receiving refrigerant fromsaid compressor, means to unload said motor, an initiating member ofmagnetic material adapted to be disposed in the leakage field of saidmotor and to be raised in opposition to the force of gravity uponincrease in strength of the magnetic leakage field of said motor, andmeans whereby the initiating member actuates the unloading means inresponse to leakage field variations.

11. In a refrigerating system, a compressor, an electric motor fordriving said compressor, an evaporator for receiving refrigerant fromsaid compressor, means to unload said motor, an annular member ofmagnetic material adapted to be disposed below the motor and in theleakage field thereof and to be raised in opposition to the force ofgravity upon increase in strength of the magnetic leakage field of saidmotor, and means whereby the annular member actuates the unloading meansin response to leakage field variations.

12. In a refrigerating system, a compressor, an electric motor fordriving said compressor, an evaporator for receiving refrigerant fromsaid compressor, an unloading valve for said compressor, and means foractuating said valve including an annular member of magnetic material solocated below said motor as to be raised against the force of gravityupon increase in strength of the magnetic leakage field of said motor.

CARL E. L. LIPMAN.

